Suspension polymerization method for preparing elastomeric hydrocarbon interpolymers

ABSTRACT

A process is provided for preparing ethylene-propylene-diene terpolymers in suspension employing a normally liquid hydrocarbon such as cyclohexane and liquid propylene, the amount of liquid hydrocarbon ranging from 10 to 50 percent by volume and liquid propylene ranging from 50 to 90 percent by volume, this polymerization system resulting in no reactor fouling.

United States Patent Schrage et al.

[ 51 *June 20, 1972 [54] SUSPENSION POLYMERIZATION METHOD FOR PREPARINGELASTOMERIC HYDROCARBON INTERPOLYMERS 3,225,021 12/1965 Erchak..260/93.7

3,326,883 6/ l 967 Kelley .....260/94.9

3,520,859 7/1970 Schrage et al ..260/882. D

OTHER PUBLICATIONS [72] Inventors: Albert Schrage, East O J l ErnestEncyclopedia of Polymer Science and Technology Vol. 3; pp,

Schoenberg, B fl ld b h of N 833- 834, 838, 852- 854 and 856;Cohesive-Energy Density; lnterscience Publishers; New York 1966) TPl56.P6 E6 [73] Assignee: Dart Industries Inc., Los Angeles, Calif.

[ Notice: The portion of the term of this patent subjg gfg gffig'jgr xgg {a S 3 :25 to July 1987 has been dis- AnomeyFred S. Valles, RichardA. Dannells, Jr. and Robert P. Whipple [22] Filed: June 27, 1968 21Appl. No.: 740,692 [57] ABSTRACT A process is provided for preparingethylene-propylene-diene terpolymers in suspension employing a normallyliquid [52] US. Cl. ..260/80.78, 260/882 R hydrocarbon h as l h e dliquid propylene, the [5 1] Int. Cl ..C08f 15/04, C08f 15/40 amount fliquid hydrocarbon ranging f 10 to 50 percent Fleld seal'dl R, by volumeand liquid propylene ranging from to percent 0/ D by volume, thispolymerization system resulting in no reactor fouling. [56] ReferencesCited 10 Claims, 1 Drawing Figure UNITED STATES PATENTS 3,205,216 9/1965McManimie ..260/94.9

Z I cn E Area A g a e 5-; 5 E F D 1 G s W l LL] s'.o 7:0 8lO 9T0 |o'.o6.7 9 3 Solubility Parameter PATENTEDJum 1972 3.671505 EPR SolubilityArea B Area C U (G I 6.0 71o 9T0 16.0 6.7 9.3 Solubility Porclmeier -p-ALBERT SCHRAGE JULE'S E. SCHONBERG IN VEN TORS BY Zm I ATTORNEYSUSPENSKON POLYMERIZATION METHOD FOR PREPARENG ELASTOMERIC HYDROCARBONHNTERPOLYMERS FIELD OF INVENTION This invention relates to a suspensionpolymerization method for preparing linear synthetic elastomericinterpolymers. The invention relates more specifically to an improvementin a method for preparing linear synthetic elastomeric interpolymers bythe employment of a transition metal compound activated with anorganometallic reducing agent wherein the elastomeric interpolymer isformed in discrete or substantially discrete particle form in a novelsuspension polymerization medium with agitation and wherein reactorfouling is substantially eliminated.

PRIOR ART In the commercial manufacture of linear synthetic elastomericproducts from two or more olefinically unsaturated hydrocarbons, it hasbeen taught to employ as a solvent a normally liquid hydrocarbon such ashexane or heptane and to interpolymerize olefinically unsaturatedmonomers while employing as catalysts transition metal halides such asvanadium or titanium compounds activated with trialkylaluminum compoundsor alkyl-aluminum halides and hydrides. Conversion of the olefinicmonomers to the interpolymer product in this type of process is usuallylimited to from to percent total solids due to the formation of a highlyviscous phase which is referred to in the art as a rubber cement. Thehigh viscosity of this rubber cement poses certain problems, chiefly,difficulty in agitation, and poor mass transfer leading to polymerinhomogeneity and poor heat transfer properties. The low total solidsconversion thus required for low viscosity and easy handling adverselyaffects production rate and costs of manufacture.

In the above described commercial methods for manufacturing linearsynthetic elastomers, the interpolymerization reactions are carried outat temperatures below 45 C, usually below 20 C and frequently attemperatures of about 0 C or below, since some of the more activevanadium catalysts have a longer life at such temperatures. At thesepolymerization temperatures, therefore, refrigeration is required andthis obviously increases the cost of investment. Low polymerizationtemperatures are also required in some polymerization processes in orderto prevent interaction between the catalyst and certain chlorinateddiluents which have also been described as useful in the literature.

The recovery of the rubber cement formed in the foregoing manufacturingprocess usually involves a costly and difficult polymer coagulation stepand a concomitant purification step for recovery of the diluent.

in apparent attempts to overcome some of the difficulties inherent inthose processes indicated above, the literature reports that prior artworkers have prepared elastomeric linear interpolymers in suspensionfonn, for example, by using one of the monomers as the diluent in liquidform. Such a technique for preparing an ethylene-propylene rubber isdescribed in British Pat. No. 898,261. in that patent, the preparationof an ethylene-propylene copolymer elastomer is described carrying outthe polymerization employing propylene in the liquid phase at preferredpolymerization temperatures of from l0 to l00 C. The employment ofliquid propylene as the sole diluent in the preparation of anethylenepropylene rubber has, however, certain disadvantages such as therequirement of the low temperatures and the fact that such a process hasbeen found to result in heavy reactor fouling, that is, adhesion ofinsoluble polymer to reactor surfaces, as illustrated in Example 2 ofthe instant specification.

Another attempt to overcome difficulties inherent in the solutionprocess is the suspension polymerization process conducted in methylenechloride as described in U.K. Pat. No. 925,468. In that patent thepreparation of ethylene-propylene diene terpolymer elastomer isdescribed carrying out the polymerization in organohalogen solventsresulting in low molecular weight rubbers, however, because the solventsact as chain transfer agents. Furthermore, for reasons to be discussedbelow, only low concentrations of propylene can be used in this systemgiving low polymerization rates and low polymer productivity per weightof catalyst resulting in a high cost process.

STATEMENT OF INVENTION An object of this invention is to provide animproved process for the manufacture of linear elastomeric interpolymersin a suspension to form discrete rubbery particles.

A further object of this invention is to prepare linear syntheticelastomeric interpolymers in a novel diluent system, which systemenables the manufacture of such interpolymers in discrete particle form.A specific object of this invention is the manufacture ofethylene-propylene rubbers, and terpolymers of ethylene-propylene and athird monomer containing multiple unsaturation whereby the disadvantagesof the prior art methods of preparing these copolymers and interpolymerssuch as reactor fouling are substantially eliminated.

Accordingly, an improvement is provided herein in a process forpreparing a linear synthetic elastomeric interpolymer wherein propyleneand ethylene are interpolymerized with at least one other unsaturatedhydrocarbon monomer in the presence of a transition metal compound andan organometallic reducing agent as a catalyst, the said improvementcomprising conducting said interpolymerization in a diluent systemcomprising (a) a normally liquid hydrocarbon in an amount of from 10 to50 volume percent and (b) liquid propylene monomer in a correspondingamount of from 50 to 90 volume percent of the total liquid diluentsystem therein, and recovering from said interpolymerization saidelastomeric interpolymer in discrete particle form. This invention alsoencompasses the use of a normally gaseous aliphatic hydrocarbon of fromthree to five carbon atoms in liquid form and in admixture with normallyliquid hydrocarbons as will be illustrated hereinafter. By the termmonomers or hydrocarbon monomers containing multiple unsaturation asemployed in this specification, it is intended to meanvthose monomerswhich are used to impart olefinic unsaturation to elastomericinterpolymers such as ethylene-propylene terpolymers.

The attached drawing, which forms a part of this invention, illustratesin graph form curves which illustrate solubility parameters, typicallyof the system ethylene-propylene rubber and solvents or diluents of thisinvention. More will be said about this FIGURE later.

In the process of this invention, the selection of the diluent system iscritical. As one component of the diluent system, there is selected anormally liquid hydrocarbon which can be employed in an amount of from10 to 50, preferably 20 to 30 volume percent and as the secondcomponent, preferably a reactive hydrocarbon in liquid form in acorresponding amount of from 50 to 90, preferably to 70 volume percent.Substantially inert normally liquid hydrocarbons can be pentane, hexane,cyclohexane, benzene and many others which will be describedhereinafter. it has been found that by the employment of the diluentsystem above that this system unexpectedly gives small highly swollenpolymer particles. The reaction may be continued as a very fluid slurrythat can be carried to a solids content of about 15 to 20 percent byweight (I lblgal) the rate being limited by cooling capacity. There arecertain specific and unique advantages to the process herein and thesewill be described in more detail later on.

The selection of the normally liquid hydrocarbons herein has beendictated to some extent by the solubility parameters" of the particularhydrocarbon in point. Solubility parameter is a measure of likeness orcompatibility of liquids. Thus, two liquids with similar solubilityparameters are, in general, compatible while two liquids with widelydiffering solubility parameters are, in general, incompatible andprobably immiscible. Solubility parameter for a volatile liquidneopentane (2,2-dimethylpropane) 6.117 Z-methylbutane (isopentane) 6,7472,2,4-trimethylpentane (isoctane) 6.849 2,2,3trimethylbutane 6.942n-pentane 7.02 n-hexane 7.24 n-heptane 7.42 n-octane 7.55 n-nonane 7.648n-decane 7.722 methylcyclohexane 7.82 n-hexadecane 7.99 cyclooctanecyclononane and methyl substituted cyclopentane 8.10 cyclohexane 8.18decalin 8 .30 n-propylbenzene 8.65 p-xylene 8 .75 m-xylene 8 .80mesitylene 8.80 ethylbenzene 8.80 toluene 8 .9 1 o-xylene 9.00 benzene9.15 tetralin 9.50

The solubility parameters of normally gaseous hydrocarbons at 25 Caccording to this invention are:

propane 6.2 isobutane 6.3 butane 6.6 neopentane 6.1 isopentane 6.7

The solubility parameter of propylene is 6.1 and butene-l is 6.7 whileothers are known.

The solubility parameters of elastomers is determined differently fromthose of volatile liquids. Thus, for polymers, the solubility parameterscan be obtained from swelling measurements on crosslinkecl polymers insolvents of varying solubility parameters. An experimental method forsuch determinations is described by T..l. Dedek and F. Bueche in Journalof Polymer Science, Part A, Vol. 2, pages 811 to 822 (1964).

In general, the solubility parameter of hydrocarbon elastomericinterpolymers lies in the range of 7.8 to as high as about 8.8 dependingon the components of the system. The solubility parameter for anethylene-propylene rubber containing 53 mole percent ethylene is 7.9,for example. When a third component is added to introduce unsaturationsuch as a non-conjugated diene, the solubility parameter of theresulting elastomer changes. Thus, with of dicyclopentadiene present inthe molecule the solubility parameter is about 8.0, with 10 percent itis about 8.1 and with percent it is around 8.2 (as shown in the drawingattached to which reference has heretofore been made). Solubilityparameters are important and in order to understand this concept alittle better, reference is again made to the Figure.

The selection of a diluent system for a suspension polymerizationprocess as set forth in this specification, as well as certain of thepolymerization conditions, are critical in that the diluent system andcertain reaction conditions must be capable of producing a particle forminterpolymer with minimum reactor fouling. As an example, the use ofbutane (solubility parameter 6.6) as the sole diluent in anethylenepropylene interpolymerization results in the formation of aviscous cement and not discrete particle form rubber. However, where theinterpolymerization is carried out in combination with propylene(solubility parameter 6.1) in liquid form and at least 15, preferably 20percent by volume of said propylene is maintained in liquid form duringthe entire reaction, then the end result is the production of a particleform elastomer with minimum or no reactor fouling. The reason for theseresults is not entirely understood, but the operability of the preferreddiluent system has nevertheless been established.

Referring to the figure as indicated above, Area A represents the regionof complete solubility of rubber in the solvents having solubilityparameters in the range of 6.7 through 9.3 as noted on the abscissa ofthe graph. It will be noted that the solubility parameter ofethylene-propylene rubber is about 8.0. Area B is an area of partialsolubility with a solubility parameter range of 6.0 to 6.7 while Area Cis another area of partial solubility with a solubility parameter rangeof 9.3 to 10. In accordance with this invention, it has been found thatreactor fouling can be eliminated substantially and the rubber producedin particle form if the solubility parameters of the solvent or diluentsystem differ from the solubility parameter of the elastomeric system bybetween 1.3 to 2.0 units but preferably 1.30 to 1.60. Within this rangethe process eliminates reactor fouling and such is eliminatedspecifically below the liquid reaction level. Thus in the drawing, theportion of Area 13 between 6.0 and 6.7 represents an area in whichrubbery beads or particles can be obtained in the polymerizationreaction. If the solubility parameter of the solvent is maintained inthe part of Area B, then the rubbery material will exist in a highlyswollen state as it is formed in the mixture (this is verified by takingthe finished rubber and shaking it in such a solvent for several hoursuntil equilibrium is reached). Further, not only are the rubberparticles in a highly swollen state but they also break up during thereaction into very small pieces and such breaking up occurs either dueto the stirring means in the vessel or the polymerization activitywithin the vessel, or both. One of the unique consequences of thephenomenon above is the result that the rubber particles do not adhereto glass or metal surfaces of the particular container in which thepolymerization is being carried out nor do they fuse with each other onstanding. The mixture, even if allowed to settle, is essentiallydispersable by gentle shaking and this is important since it shows thatduring the polymerization process the rubber being formed will notcoagulate or stick to the vessel walls thereby causing operationaldifficulties.

Should the solubility parameter of the diluent system exceed that of therubber on the C side area of the Figure by 2.0 units, or be less thanthat of the rubber on the B side area by the same amount then thepolymer formed will be completely insoluble and will not swell up ordisperse. When polymerization is attempted in such a medium, the rubberthat is formed immediately precipitates and it is deposited as atenaciously adhering coating over the entire reactor surface. In theevent that the difference in solubility parameter between diluent andrubber is less than 1.3 units, then the polymer dissolves completely toa highly viscous cement and conditions of solution polymerizationprevail.

It is to be noted again referring to the aforementioned FIGURE and UK.Pat. No. 925,468 which carries out suspension polymerizations insolvents such as methylene chloride that the process is conducted inArea C of the Figure. In this case the solvent, methylene chloride, hasa solubility parameter of about 9.7.

Although in principle a suspension polymerization can be conducted inArea C, the system sufiers from significant practical disadvantages, forexample, the solvents used, the organo-halogen compounds, react in thepolymerization to reduce molecular weight and this gives a polymer withundesirably weak physical properties as well as a polymer which cannotbe extended with oil and loaded with carbon black to give a low costcompounded rubber. Furthermore, and very importantly, only a very lowpropylene concentration can be used in this system, otherwise thesolubility parameter of the mixture is shifted from area C to area Awhich converts the suspension polymerization to solution polymerization.A consequence of the allowable low propylene concentration is that lowrates of polymerization and low catalyst productivities are obtainedresulting in high production costs.

Evidence of the shift to a solution system, that is, that upon increasein propylene concentration the operational area is caused to shift fromC to A, is given in page 7 of the cited UK. patent, lines 31 through 38which state partially as follows: As the concentration of hydrocarbonmonomers increases the copolymer tends to become partially or completelysoluble in reaction medium In the process of this invention, asheretofore noted, the solids conversion, that is, the amount of totalsolids that can be readily handled is at least 5 to 10 weight percentwithout encountering any problems and such a percent conversion forms areadily stirrable slurry which does not present any heat transferproblems. Additional advantages will be indicated hereinbelow withrespect to this observation.

PREFERRED EMBODIMENTS in accordance with the above it is preferred tooperate in the process herein with a hydrocarbon diluent system whichwhen mixed with substantial amounts of propylene liquid has a solubilityparameter in the range of 6.0 to 6.7 units, that is, area B in thedrawing. Although there are some diluents with solubility parametersabove 8.0, such as 9.0 and 9.5, which can be used in accordance withthis invention, that is, operation in area C, the more readily availableand cheaper hydrocarbons indicated hereinbefore are preferred and as aconsequence emphasis has been placed on this technique ofinterpolymerization.

The effect of the solubility parameter of the system, that is thecriticality is readily observed by departure from the preferredsolubility parameters indicated above. It will be noted that liquidpropylene with a solubility parameter of 6.1 is employed in majorquantities herein and that by employing a liquid hydrocarbon thesolubility parameter of the system can be raised, depending on theamount of hydrocarbon used, to 6.7 or even higher depending on thesolubility parameter of the rubber being made since the solubilityparameter of a liquid mixture is the arithmetical average of thesolubility parameters of the constituents based on their volumetricproportions. Various diluent systems will be illustrated in the Examplesof this invention.

The preferred liquid diluent monomer which of course also enters intothe interpolymerization is propylene.

in the discussion above concerning the liquid or gaseous monomers andtheir solubility parameters, emphasis has been placed on those monomersuseful in a two-component elastomeric system such as ethylene-propylenewith little or no reference to the use of a third monomer to formterpolymers. When the third monomer in an elastomeric terpolymer ishighly reactive, as in the case of dicyclopentadiene and othernorbornenes, it is employed in minor amounts, that is in amountssufficient only to impart unsaturation for sulfur curing (usually in theranges of about 5 to 10 percent by weight, based on the final productmakeup) so that the solubility parameter of the third monomer per sedoes not substantially affect the combined role of the inert diluentbecause it is present in a very small proportion. However, the presenceof substantial amounts of the third monomer in the rubber can affect thesolubility parameter of the rubbery component and take it out of thepreferred 1.3 to 2.0 difference in solubility parameter units. When thishappens the diluents are adjusted to bring the solubility parametersback to the preferred range. Thus, it has been found that a mixture ofnormal butane and propylene (in a volume ratio of 70:30) can be used togive a non-fouling suspension polymerization to form ethylenepropylenecopolymer and ethylene-propylene terpolymer, the latter containing up to5 weight percent of diene. (Copending application Ser. No. 521,236 filedDec. 9, 1965, now U.S. Pat. No. 3,520,859. discloses systems of thistype.) However, when this latter figure is exceeded the same suspensionpolymerization is heavily fouled indicating a shift of the solubilityparameter of the rubber to a higher value. This, for example, isindicated in the drawing where Curve E represents an ethylene-propyleneterpolymer with 5 weight present diene hydrocarbon as the minorcomponent and the solubility parameter indicated is about 8.0. Uponincorporation, however, of 10 weight percent diene to theethylene-propylene rubber system, the solubility parameter increases to8.1 as shown in Curve F while the incorporation of 15 weight percentdiene as shown in Curve G increases the solubility parameter of thesystem to about 8.2. However, the system can be restored to annon-fouling suspension polymerization by the addition of about 10% byvolume of benzene which has a solubility parameter of 9.15. The additionof benzene shifts the solubility parameter of the diluent of the diluentmixture to a higher value thereby once again bringing the reaction intoarea B of the Figure. An example illustrating this concept will bepresented hereinbelow.

As can be understood from the above, therefore, systems wherein anormally gaseous paraffinic hydrocarbon such as propane or butane inliquid form is employed for a suspension reaction, the amount of saidhydrocarbon employed being from about 15 to volume percent can bemodified to give non-fouling suspension polymerization reactions, wheresuch occurs due to the use of higher amounts of diene in a terpolymer,by incorporation of a normally liquid hydrocarbon diluent such as anaromatic hydrocarbon of a solubility parameter of about 9.0 such asbenzene. The amount of such normally liquid diluent to be incorporatedin such a system should be sufficient only to restore it to anon-fouling type and ranges from about 5 to 15 percent by volume (orhigher) of such diluent. Also, as heretofore noted, while percent solidsconversion can be from 5 to 15 percent, it is preferred in this systemto carry the percent conversion to from 5 to 10 percent to obtainexcellent operation.

lnterpolymers containing at least three unsaturated hydrocarbon monomerscan likewise be prepared according to the process herein. In theinstance of interpolymers of the type described herein, a third compoundwhich is an acetylenic hydrocarbon such as acetylene itself or amultiple unsaturated hydrocarbon monomer such as dicyclopentadiene andalkyl derivatives can be incorporated in appropriate amounts to impartunsaturation to the rubbery elastomer as is known in the art. Bridgedring hydrocarbons in general are useful herein specifically thosecontaining one unsaturation in the bridged ring molecule and anotherunsaturation external thereto. Typical of the third componenthydrocarbon monomers are the following:

a. Monocyclic diolefins such as cis, cis-l, 5-cyclooctadiene1,4-cycloheptadiene b. Polyalkenylcycloalkanes such astrans-1,2-divinylcyclobutane; 1,2,4-trivinylcyclohexane c. Bicyclicdienes such as bicyclo (4.3.0) 3,7-nonadiene;

bicyclo (4.2.0.) 2,7-octadiene; bicyclo (3.2.0) 2,6-heptadiene;

d. 2-alkylnorbornadienes having about 8-24 carbon atoms such asZ-methylnorbornadiene, 2-ethylnorbornadiene, 2-propylnorbomadiene and,in general, those norbornadienes in which the alkyl group contains from[-17 carbon atoms (see U.S. Pat. No. 3,063,973) and e.5-alkenyl-2-norbomenes such as 5-(1'-butenyl-2-norbornene; 5-( l-propenyl)-2-norbornene; 5-(2'-butenyl )-2- norbomene;5-(2-ethyl-2-butenyl)-2-norbornene and 5-(2'-heptyl-l-undecenyl)-2-norbomene, etc., and 5-methylene-Z-norbornene; 5-ethylidene-2-norbomene;

Ternary interpolymers of ethylene and propylene and in ratios between3:1 and 1:3 and (i) another alpha-olefin of the formula CH, CHR where Ris an alkyl radical containing from 2-8 carbon atoms and is present inan amount of 2 to 20 mole present of the interpolymer; (ii) aliphaticnon-conjugated dienes having the structure wherein R is an alkyleneradical, R R and R are selected from the group consisting of H andalkyl, and ]R to R are selected so that the diene has from 6 to 22carbon atoms (see U.S. Patent 3,166,517); e.g., l,4-hexadiene,1,6-octadiene,

1,5-hexadiene (see US. Pat. No. 2,933,480), etc.

In general, the process of this invention is applicable to thepreparation of two, three, four or more component elastomers, that isany of the known elastomeric compositions known to the art. Since thisinvention is concerned with the process of preparing these compositionsand not with novel compositions per se, detail concerning such is knownto those skilled in the art.

Any of the well known catalysts for preparing amorphous linearinterpolymers known to the art can be employed in the process herein.Such catalysts include the titanium halides such as titaniumtetrachloride activated with metallic organic reducing compounds such astrialkylaluminum compounds, alkylaluminum halides and hydrides. Suitablecatalysts for the process herein are the vanadium compounds such as VOClVCl and vanadium tris(acetylacetonate), alkylchlorovanadates,trialkyl-vanadates such as triethyl vanadate, tri-n-propylvanadate and,in general, any of the catalysts well known in this art includingmixtures of these and including adjuvants thereto or additives such asamines. Catalyst concentrations required to carry out any polymerizationare necessarily those which are sufficient for initiation purposes andsufficient to perform such economically, suitable examples being offeredhereinbelow.

Molecular weight control or desired molecular weight distribution of theproduct can be effected by varying catalyst component mole ratios or bythe use of hydrogen or any other known means to the art.

The polymerization conditions in accordance with the process herein canbe varied considerably from those of the prior art. For example, a widerrange of polymerization temperatures can be used since heat transfer isnot a problem in this process as compared to heat transfer duringpolymerization and processing of a viscous cement.

The general polymerization procedure is carried out as follows: Areactor is flushed with ethylene and pressured with ethylene to 90 psig.The reactor is then charged with 0.25 ml of diethylaluminum monochloride(DEAC) and propylene and the solvents are charged in appropriate ratiossuch as:

hexane 27% propylene 73%; cyclohexane 25% A an Iodine Number of about10). The reactor contents are then brought to 22C with stirring and a0.029 molar solution of VCl in hexane is used. The VCI, addition isbegun along with diene (as a 30% solution in hexane or other solvent)and monomer gas feed (55mole percent ethylene and 45 mole percentpropylene). The pressure is maintained constant at about 130 psig byadjustment of gaseous monomer feed. The VCl solution and diene solutionfeed rates are each about 0.4 ml/minute. The gaseous monomer feed rateis about 1.0 gram/minute. The diene feed is varied according to thegaseous monomer flow so that approximately 0.06 gram of pure diene isadded per gram of ethylene plus propylene polymerized which correspondsto an Iodine Number of 10. The final AlzV ratio is preferably kept above10. The reaction is run for about 30 minutes at which time VCl, additionand diene addition are stopped. .The polymerization dies off in aboutminutes and isopropanol is added.

As hereinbefore noted in the process of this invention, the monoolefinscomprise a major proportion of the reactants which preferably range fromto percent by weight, the remainder consisting of a third monomer whenterpolymers are prepared. Generally, the mono-olefins are incorporatedin equimolecular proportions, but variations are permissible as long asan amorphous elastomeric product is the result of such a polymerization.

The elastomers formed from only two alpha-olefins as is known in the artcan be crosslinked with peroxides or with peroxides plus sulfur and theresulting vulcanizates have excellent elongation and tensile strength.

The elastomers prepared according to the process of this inventioncontaining olefinic unsaturation have vulcanizing properties similar tothose of natural rubber. The olefinic unsaturation of theseinterpolymers is expressed by an iodine number (lCl absorbed expressedas grams of iodine absorbed per grams of rubber) which is an indicationof adequate curability and can range from at least 3 to not more than50, preferably 5 to 20 (determined according to the method described byTS. Lee, [.M. Kolthoff and Ethel Johnson, Analytical Chemistry," Vol.22, pages 995 to 1001 (1950.). These interpolymers have intrinsicviscosities (defined and determined according ASTM D-l60l-61) in Decalinat C of between 0.5 and 7.0 and contain from about 1 to 15, preferably 1to 4 mole percent of a multiple unsaturated hydrocarbon interpolymerizedusually with an alpha-olefin pair such as ethylene and propylene.

The Mooney viscosity of the products of the process of this inventioncan range from 20 to 150, preferably 30 to 90, as determined with aMooney viscometer at 212 F (ML-4) in accordance with ASTM D-927-55T.

The polymerization procedure in cyclohexane or benzene to specificallydemonstrate diluents is carried out as follows:

The polymerization is carried out in a 2.5 l glass autoclave equippedwith a magnetic stirrer assembly and a coil of steel tubing suspended inthe vapor phase to provide reflux cooling. The reactor is flushed withethylene and pressurized to 90 psig with ethylene and then to 92 psigwith hydrogen. The reactor is then charged with ml of cyclohexane, 0.17ml of diethylaluminum chloride, 3.8 ml of methyldicyclopentadiene (thediene used to impart unsaturation in the rubber) and 400 m1 ofpropylene. Stirring is begun and the temperature is brought to 20 C.Additional ethylene is added to bring the pressure to 148 psig. Theterpolymerization is started by feeding a 0.0134 M solution of VCl inhexane. Gaseous ethylene, liquid propylene, liquid diene (as a 50percent by volume solution in n-hexane) and diethylaluminum chloride (asa 3.5 percent by volume solution in n-hexane) are fed to the reactor atrates calculated to keep the diethylaluminum chloride concentration andthe monomer ratios constant. The initial solvent mixture has asolubility parameter of about 6.85 and the rubber dissolves to form aviscous cement. Excess propylene over that polymerized is fed into thereactor and so the solubility parameter of the diluent drops until therubber precipitates to form a suspension at which point the mediumsundergo a sudden decrease in viscosity. Keeping the reaction mediumsomewhat viscous as in the above procedure prevents the rubber fromadhering to protuberances such as thermocouples in the reactor and thusprevents fouling.

The reaction is stopped after 81 minutes by the addition of a solutioncontaining 1 gm. of 2,6-di-t-butyl-4-methy1phenol Ionol) in 5 ml. ofisopropyl alcohol. At this stage the slurry contains 16 percent byweight of solids and the diluent contains 18% by volume of cyclohexanewhich corresponds to a solubility parameter of about 6.56. Deionizedwater (500 ml) is added to the reactor and the mixture is stirred forone hour. The water is removed through a A-inch stainless steel dip tubethat is immersed near the bottom of the reactor and the slurry is giventhree rinses in the above manner with 500 ml of water per rinse. Therubber is recovered and vacuum dried. The results of the polymerizationare summarized below:

Diene feed 0.13 mllmin. Propylene feed 5.1 rnI/min. Diethylaluminumchloride feed 1.3 X 10" ml/min.

1.4 X mmole/min.

108 g. 4480 g. rubber/g. -VC1, 3.7

vol, feed Yield Productivity Inherent viscosity The above proceduregives small highly swollen polymer particles at the start of thepolymerization. After about 3 per- 10 cent by weight of polymer has beenformed, the reaction becomes viscous and additional propylene is added,which causes the particles to enlarge and harden, and results in a veryfluid slurry that can be carried to a solids content of about -20percent by weight (1 lbs/gal.) in about two hours, the rate beinglimited by cooling capacity. Propylene is added during the reaction,about 400 ml. being added in about two hours. With the benzene/propylenesystem, the starting benzene concentration is 27% and the finalconcentration is about 19%. The comparable values for cyclohexane areclose, 31% and 21%.

The following examples illustrate this invention with moreparticularity.

EXAMPLE 1 Prior Art Preparation of Ethylene-Propylene-DicyclopentadieneTerpolymer by Solution Polymerization in n-I-Ieptane This exampleillustrates the preparation of an amorphousethylene-propylene-dicyclopentadiene terpolymer by a conventionalsolution polymerization in n-heptane.

A 1.5 liter stainless steel stirred autoclave was charged, under anargon atmosphere, with 600 ml of dry n-heptane, 200 ml of liquidpropylene, 8.6 g. of ethylene and 1.0 ml (8.8 millimoles) ofethylaluminum sesquichloride. The reactor was heated to and maintainedat 45 C and 7 ml ofa 0.075 M (0.52 millimoles) solution of VOCl inn-heptane and 11 ml of a 15 volume percent solution of dicyclopentadienein n-heptane were added over a 21 minute period. During thepolymerization, the reactor pressure was maintained at 108 psig by theaddition of a monomer mixture containing 56 mole percent ethylene and 44mole present propylene. The reaction was continued for an additionalnine minutes and then ml of a 5 percent solution of Ionol in isopropanolwas added to deactivate the catalyst. A clear viscous solution wasobtained. The terpolymer wasprecipitated in a Waring blender with 1liter of isopropanol containing 2.0 g. of Ionol. The rubber was washedwith the isopropanol-stabilizer mixture and vacuum dried.

EXAMPLE 2 Prior Art Preparation of Ethylene-Propylene Copolymer BySuspension Polymerization in Liquid Propylene This Example illustratesthe preparation of an amorphous ethylene-propylene copolymer by asuspension polymerization in liquid propylene.

A 1.5 liter Teflon lined stirred autoclave was charged with 500 ml ofliquid propylene, 13.4 g. of ethylene and 1.0 ml (8.8 millimoles) ofethylaluminum sesquichloride. The temperature was set at 25 C and 4 mlof 0.036 M (0.14 millimoles) solution of VOCl in n-pentane was addedover a 25 minute period while the pressure was maintained between170-185 psig with the addition of ethylene. The reaction was continuedfor an additional 7 minutes, after which 500 ml of isopropanol wasadded. The product consisted of large rubbery beads. However, a thicklayer of rubber was attached to the Teflon coating. The product waswashed with an Ionolisopropanol mixture (2.0 g. Ionol/l) and vacuumdried.

Yield 32 grams Inherent Viscosity (decalin at 135C) 6.8 PercentInsoluble in Cyclohexane at Room Temperature 0 EXAMPLE 3 The reactor inthis Example was flushed with ethylene and pressured with ethylene to 90psig. The reactor was then charged with 0.25 ml of DEAC, 183 ml ofcyclohexane and 550 ml of propylene, or with 150 ml of benzene and 600ml of propylene or with 200 ml of hexane and 525 ml of propylene.Methyldicyclopentadiene (2.2 to 7.4 ml) was then added and the reactorcontents brought to 22 C with stirring. A 0029M solution of VCl, inhexane was used as the catalyst and VCl addition was begun along withdiene (as a 30 percent solution in hexane) and monomer feed gas molepercent C and 45: mole percent C The equilibrium reaction pressure was,about 130 psig and the pressure was maintained constant dur-' ing thereaction by adjustment of gaseous monomer feed. The VCl solution anddiene solution feed rates were each about 0.4 ml/min. The gaseousmonomer feed rate was about 1.0 gram/min. The diene feed was variedaccording to the gaseous monomer feed so that approximately 0.06 to 0.15g of pure diene was added per gram of ethylene plus propylenepolymerized which corresponds to an Iodine Number of 10 to 25. The finalAl/V ratio was kept above 10. The reaction was run for about 30 minutesat which time VCl addition and diene addition were stopped. Thepolymerization died off after about 15 minutes and isopropanol wasadded.

Table I below illustrates a series of runs carried out in accordance with the above.

TABLE I.POLYMERIZATIONS IN LIQUID I-IYDROCARBONS Yield 29 grams InherentViscosity (decalin at I35C) 2.9 Percent Insoluble in Cyclohexane at RoomTemperature 0.2 Iodine Number 5.1

The terpolymer prepared in accordance with this Example formed as aviscous cement as indicated and the conversion was low.

In the above Table I in all of the runs the polymer was recovered inslurry form and no difficulty was encountered with respect to foulingbelow the liquid level.

The resulting fluid slurries from the polymerization above can easily becooled by refluxing of the propylene. The

molecular weight as shown, gel content, catalyst productivity andunsaturation (diene reactivity) are the same for both,

cyclohexane and benzene. Cyclohexane is presently the preferred diluentfor the process of this invention.

The next three Examples illustrate that small changes in the solubilityparameter of the polymer and the diluent can have a pronounced effect onthe polymerization.

EXAMPLE 4 Preparation of Ethylene-Propylene-Diene Terpolymer bySuspension Polymerization in Butane-Propylene Mixture A 2.5 literstirred glass autoclave was flushed with ethylene and pressurized withethylene to 55 psig. The reactor was then charged with 1,050 ml ofn-butane, 450 ml of propylene, 0.53 ml of diethylaluminum chloride and7.8 ml of methyldicyclopentadiene. Stirring was begun, the temperaturewas lowered to 21 C and the polymerization started by feeding a 0.028 Msolution of VCl in n-hexane. The monomer concentrations were heldconstant by maintaining constant reactor pressure with a gaseousethylene (55 mole percent)-propylene feed mixture and by feeding a 42percent by volume mixture of methyldicyclopentadiene in n-hexane.Towards the end of the polymerization the rubber plated out onto thereactor surfaces. The solubility parameter of the diluent wasapproximately 6.46. The VCl, feed was stopped after 42 minutes ofreaction time and the monomer feeds were stopped after 52 minutes. Thediluent was displaced with a 0.2 percent solution of2,6-di-t-butyl-4-methylphenol. in isopropyl alcohol. The rubber waswashed with fresh iso-propyl alcohol-antioxidant mixture and vacuumdried at 35C.

The rubber was foundto have an Iodine Number of 21.2. When anethylene-propylene-diene terpolymer was prepared under identicalconditions but with an Iodine Number of 10, a, non-fouling suspensionpolymerization resulted. This indicates that the diene shifts thesolubility parameter of ethylenepropylene rubber to a higher value.

EXAMPLE 5 l Preparation of Ethylene-Propylene-Diene Terpolymer bySuspension Polymerization in a Butane-'Propylene-Benzene Mixture v Theprocedure for this Example is substantially the same as. in Example 3except that the diluent consisted of 620 ml of nbutane, 300 ml ofpropylene and 80 ml of benzene. A non fouling suspension polymerizationresulted. The solubility parameter of the diluent was approximately6.66.

EXAMPLE 6 Preparation of Ethylene-Propylene-Diene Terpolymer by SolutionPolymerization in a Butane-Propylene-Benzene Mix ture The procedure forthis Example is substantially the same as in Example 3 except that thediluent consisted of 830 ml of n-! butane, 400 ml of propylene and 160ml of benzene. A viscous cement formed. The solubility parameter of thediluent wasapproximately 6.76. A comparison of Example 4, 5 and 6 showsthat the substitution of increasingly larger amounts'of butane bybenzene progressively raises the solubility parameter of the system froma region of insolubility where heavy fouling occurs to a region which isoptimum for suspension polymerization and finally to a region wherecomplete solution occurs.

The results of Examples 4, 5 and 6 are summarized in the Table below. I

TABLE 11 Example 4 5 til vol; feed (mmoIe/min.) 6. 1 10- 2. 5))(10' 7.2X10? Diene feed (ml./min.) 0. 13 0.098 0. 084 Ethylene-propylene feed(1. I 1. 1 0. 82 0.941 Yield (g.) 73 6 Productivity (g. polymer/g. V014)1000 1610 680 Inherent viscosity 2. 7 3. 7 2. 6 Iodine number 21. 2 19.0 14.8

Percent gel In accordance with this invention, it has been foundpossible to raise the catalyst productivity by raising the partialpressure of ethylene in the diluent system. In reactions run to aboutthe 5 weight percent solids level, a productivity of about 10,000-12,000 was reached before encountering crystallinity. It is seentherefore that the system herein possesses certain out-stand advantages.

The following are particular advantages of the process of thisinvention: 1. Lowviscosity leading to faster production rate, highreac-' tor throughput and better quality through:

a. Fast heat transfer by reflux cooling or cooling coils in li uid i b.l ast rnass transfer Tl l gas and ethylene gas are readily dispersiblein liquid) c. Easier stirring leading to better homogeneity with respectto polymer composition and molecular weight (small amounts of catalystand diene are readily stirred into the reaction).

2. High solids level leading to lower production costs through:

a. Less recycling of monomers and solvent b. Increased plant capacity 3.Lower costs through:

a. Lower catalyst cost (high catalyst productivity) b. Easier removal ofcatalyst residue (less to remove) High catalyst productivity ofnon-crystalline polymer is not possible in the solutionpolymerizationprocess for the following reasons. High productivity is achieved byusing high ethylene partial pressures (about 40-50 psi) but this leadsto a polymer rich in ethylene and eventually to undesirable crystal-'linity if the ethylene content of the polymer is greater than about 85mole percent. In order to stay below 85% but still enjoy the highproductivity from high ethylene pressure the reaction system mustcontain a much larger amount of propylene than can be present in thesolution process.

Although the process hereinabove has been described with ireference toparticular or preferred embodiments, it is obvious ;that modificationswithin the scope of this invention can be jmade. Thus, the normallyliquid hydrocarbons can be used in {mixtures without detrimentalresults. Other modifications will Zoccur to those skilled in this art.

' What is claimed is:

1. In a process for preparing a linear synthetic elastomericinterpolymer which comprises interpolymerizing propylene and ethylene orpropylene, ethylene and a hydrocarbon imonomer containing multipleunsaturation in the presence of a transition metal compound and anorganometallic reducing agent, the improvement which comprisesconducting the interpolymerization in suspension in a diluent systemhaving a solubility parameter which differs from the solubilityparameter of the elastomeric interpolymer by 1.3 to 2.0 units, saiddiluent system comprising (a) 50 to 90 volume percent of liquidpropylene and (b) 10 to 50 volume percent of at least one normallyliquid hydrocarbon; whereby reactor fouling is ,reduced and saidelastomeric interpolymer may be recovered in discrete particle form.

2. A process according to claim 1 wherein the solubility parameter ofthe diluent system differs from the solubility parameter of theelastomeric hydrocarbon by 1.3 to 1.6 units.

3. A process according to claim 1 wherein the diluent system comprises(a) to volume percent of liquid propylene and (b) 20 to 30 volumepercent of a normally lliquid hydrocarbon.

4. In a process for preparing a linear synthetic elastomericinterpolymer which comprises interpolymerizing propylene and ethylene orpropylene, ethylene and a non-conjugated 70Ihydrocarbon containingmultiple unsaturation in the presence bility parameter which differsfrom the solubility parameter of Q the elastomeric interpolymer by 1.3to 2.0 units, said diluent system comprising (a) 50 to 90 volume percentof liquid propylene and (b) l to 50 volume percent of at least onenormally liquid hydrocarbon; whereby reactor fouling is reduced and saidelastomeric interpolymer may be recovered in discrete particle form.

5. A process according to claim 4 wherein the normally liquidhydrocarbon is neopcntane; 2-methylbutane; isooctane;2,2,3-trimethylbutane; n-pentanc; n-hexane; n-heptane; n-octane;n-nonane; n-decane; methylcyclohexane; n-hexadecane; cyclooctane;cyclononane; cyclodecane; cyclopentane; cyclohexane; decalin; n-propylbenzene; p-xylene; m-xylene; mesitylene; ethylbenzene; toluene;o-xylene; benzene and tetralin.

2. A process according to claim 1 wherein the solubility parameter ofthe diluent system differs from the solubility parameter of theelastomeric hydrocarbon by 1.3 to 1.6 units.
 3. A process according toclaim 1 wherein the diluent system comprises (a) 70 to 80 volume percentof liquid propylene and (b) 20 to 30 volume percent of a normally liquidhydrocarbon.
 4. In a process for preparing a linear syntheticelastomeric interpolymer which comprises interpolymerizing propylene andethylene or propylene, ethylene and a non-conjugated hydrocarboncontaining multiple unsaturation in the presence of a vanadium catalystand an organometallic reducing agent, the improvement which comprisesconducting the interpolymerization in suspension in a diluent systemhaving a solubility parameter which differs from the solubilityparameter of the elastomeric interpolymer by 1.3 to 2.0 units, saiddiluent system comprising (a) 50 to 90 volume percent of liquidpropylene and (b) 10 to 50 volume percent of at least one normallyliquid hydrocarbon; whereby reactor fouling is reduced and saidelastomeric interpolymer may be recovered in discrete particle form. 5.A process according to claim 4 wherein the normally liquid hydrocarbonis neopentane; 2-methylbutane; isooctane; 2,2,3-trimethylbutane;n-pentane; n-hexane; n-heptane; n-octane; n-nonane; n-decane;methylcyclohexane; n-hexadecane; cyclooctane; cyclononane; cyclodecane;cyclopentane; cyclohexane; decalin; n-propyl benzene; p-xylene;m-xylene; mesitylene; ethylbenzene; toluene; o-xylene; benzene andtetralin.
 6. A process according to claim 4 wherein the solubilityparameter of the diluent system differs from the solubility parameter ofthe elastomeric interpolymer by 1.3 to 1.6 units.
 7. A process accordingto claim 4 wherein ethylene, propylene and a non-conjugated hydrocarbonhaving multiple unsaturation is interpolymerized.
 8. A process accordingto claim 7 wherein the normally liquid hydrocarbon is benzene, hexane ormixtures thereof.
 9. A process according to claim 4 wherein ethylene andpropylene are interpolymerized.
 10. A process according to claim 9wherein the normally liquid hydrocarbon is hexane, benzene, orcyclohexane.